I am working on a project in TileMill for the first time. I am trying to overlay a Graticule of the British national square grid.
I generated a series of LineString for the grid into PostGIS, which are stored as native EPSG:27700 (OSGB36, BNG)
I only have a small area of interest, so it is only 100x100 orthogonal lines
My grid is accurately rendered in QGIS [image:2], which I check by comparing with the "Authorative source" on Bing maps [image:1] (this is a raster of the 1:50000 British ordnance survey map reprojected to EPSG:3857 for web mapping)
When I add this layer to Tilemill image:3], it is all skewed and incorrectly re-projected from its native SRS to 900913 (Tilemill's native CRS)
I can actually see some of this issue in QGIS also, when zoomed out: [image:4 & image:6]
But when zoomed in they are accurate: [image:5 & image:7]
Unfortunately, The output from TileMill is always incorrect. [image:8]
Please could somebody give me some pointers on how to get my grid true.